1. Field of the Invention
The invention relates generally to the field of oil and gas well services. More specifically the present invention relates to a system that provides flexibility between adjacent segments of a downhole tool to enhance use of the downhole tool in deviated or slanted wells.
2. Description of Related Art
When perforating guns, are used in slanted or deviated wellbores it is often important that the tool be in a specific radial orientation. For example, orienting perforating guns in deviated wells enables the well operator to aim the shaped charges of the perforating gun at specific radial locations along the circumference of the wellbore. This is desired because the potential oil and gas producing zones of each specific well could exist at any radial position or region along the wellbore circumference. Based on the presence and location of these potential producing zones adjacent a deviated well, a well operator can discern a perforating gun orientation whose resulting perforations result in a maximum hydrocarbon production. Not only could a perforation aimed at the wrong angle not result in a preferred hydrocarbon production, but instead could produce unwanted sand production from the surrounding formation into the wellbore.
Numerous attempts have been made to overcome the problem of orienting downhole tools. These attempts include eccentrically weighting downhole tools to rotate in a certain manner or by adding external fins to the tool body to force the tool into a predefined position. Some of these can be found in U.S. Pat. Nos. 4,410,051, 4,438,810, 5,040,619, 5,211,714, 4,637,478, 5,603,379, and 5,964,294.
Many downhole tools, including perforating guns, comprise multiple elongated bodies joined end to end. If the elongated bodies are to be rotated or axially positioned, the elongated bodies must be able to rotate freely with respect to the adjacent body or bodies they are connected to. When a long downhole tool is inserted within a deviated wellbore, forces of compression and tension result along the downhole tool because of the linear deformation of the tool caused by the curved wellbore. Free rotation of the elongated bodies of a downhole tool is hindered if the tool is under compression or tension. If free rotation of the elongated bodies is hindered, they will not be able to be positioned into the desired orientation. Therefore, when the downhole tool consists of multiple perforating guns, and compressive or tensile loading binds the guns, perforations cannot be produced at the desired spots along the wellbore.
Therefore, there exists a need for a device or system in connection with downhole tools containing orienting features, where the improvement provides flexibility and prevents binding of the tool when it encounters deviated or slanted wellbores.
One embodiment of the present invention discloses a system for use in a well comprising at least two downhole tools in combination with at least one swiveling sub. The swiveling sub connects the tools end to end. The swiveling subs incorporate two sections pivotally connected to each other on one of their ends, one possible form of connection involves a ball and socket configuration. Downhole tools, such as perforating guns, are connected to both ends of the swiveling sub.
Also included in the system is a wear ring positioned radially around each downhole tool. The wear ring outer diameter is greater than the outer diameter of said downhole tool and prevents the outer diameter of the downhole tool from contacting the inner wall of the wellbore. Because the downhole tool is not in contact with the inner wall of the wellbore, the downhole tool will not experience the type and magnitude of wear as seen by downhole tools that are allowed to rub along the wellbore inner wall. Further, preventing contact between the tool and the wellbore promotes free rotation of the downhole tool because the resistance to rotation due to the wellbore inner wall is removed. Bearings are included within the invention to promote rotation of the downhole tool with respect to the swiveling subs.
The present invention further includes a detonation cord axially disposed within each section. Each section also includes a shaped charge in cooperation with an explosive device that passes explosive detonation from its detonation cord to the detonation cord disposed in an adjacent section.
One of the many features of the present invention involves increasing the flexibility of a downhole tool string to facilitate ease of insertion and retraction of the downhole tool from a wellbore. Making the downhole tool string more flexible also decreases internal compressive and tensile stresses along the string which enables individual components of the tool string to rotate about their axis with respect to the remainder of the tool string.